You double-click your clickbar? How does that help?

I looked all through the key bindings and there doesn't seem to be any way to change "clear target" or the popping up of the game menu. For now I have it sending an ESC first on my healer character. I sometimes pop up the game menu, but at least the targeting works. It turns out to not be too much of a problem as I am usually in combat when needing to heal, so I have something targeted which gets cleared.

Thanks to all your help, I have everything working now - just need a few tweaks here and there.